256 Notices of Books. |April, 
We are informed in the preface that many portions of the’ 
book have been re-written,—incumbent on the author by reason 
of the rapid extension of all the branches of the profession. So 
numerous have been-the alterations and additions that we do not 
hesitate to state that the labour of passing the book through the 
press must have cost Mr. Culley great time and close application; 
in fact, as much as would be necessary to compile the whole 
volume. Amongst the extra matter, we find an important and 
lengthy chapter on the Duplex System, which will be eagerly 
read. In this chapter, the author undertakes the explanation of — 
the question from the commencement; and in so clear and 
popular a manner does he carry the reader along with him 
through the different stages that everyone who studies the 
subject can most easily follow him. There are various methods 
of telegraphing by the duplex system, three of which are well 
known, viz., ‘‘the Bridge,” ‘the Differential,” and ‘the 
Leakage.” The two former, however, are the systems that Mr. 
Culley has treated of; the third he does not refer to, because, 
as we suppose, he does not consider it of sufficient practicability 
to deserve attention. Students, however, we are sure, would 
have been glad to have had his experience on the subject, and to 
have had an explanation of the modus operandi from his pen. 
The comprehension of the work is large and varied. It 
includes :— 
Part I., Sources of Electricity. Part II., Resistance and the 
Laws of the Current. Part III., Magnetism and Electro- 
Magnetism. Part IV., Induction. Part V., Atmospheric 
Electricity and Earth Currents. Part VI., Insulation. Part 
VII., The Construction of a Line of Telegraph. Part VIILI., 
Ordinary Testing. Part IX., Description of Instruments, © 
Part X., Submarine and Underground Wires. Addenda of 
various useful tables of reference. 
The same determination has guided Mr. Culley inthis asin former 
editions ; he has excluded from his work all theories based upon 
unproved hypotheses, and has thereby maintained its character 
as a ‘¢ practical handbook” on all matters relating to the science 
of telegraphy. Asa handbook it is unexceptional, and is rendered 
far more readable from the profuse illustrations interspersing the 
book at almost every page. Some idea may be formed of its 
rich endowment in this respect, when we mention that it contains 
over a hundred and fifty engravings, exclusive of nine full page 
illustrations, and six large folding plates of very useful designs. 
With such a work in his hands, we believe every operator on our 
lines, however backward he may be in his electrical knowledge, 
would soon acquire a sound acquaintance with the practice of the 
science, and to them, as well as to general scientific students, we — 
heartily recommend the work. 
